Background
The energy conservation requirements in code are designed to reduce energy costs of operating a home. Each conservation measure in code pays for itself through lower energy bills. While measures add to front-end cost of a home, actual cost of living in an energy-efficient home is less. The 2008 code will reduce energy costs an average of 15 percent when compared to the 2007 code, saving energy costs over the life of a home. At first, lower monthly heating bills offset higher mortgage payments. As a result, a variety of lenders can frequently offer larger loans for energy-efficient homes.
Residential building envelope requirements apply to all occupancy group R that are three stories and less in height. This group includes Apartments, Hotels, Motels, Dormitories, and certain Assisted Living facilities. While these requirements are nearly identical, they can be found in two separate building codes: Oregon Residential (ORSC) and Structural Specialty (OSSC) Codes. While this page references Tables N1101.1(1) and N1101.1(2) of the ORSC, there are similar (yet different) requirements contained in the OSSC. Until the 2010 OSSC is adopted, there will be two different residential requirements, due to the different code cycle adoptions.
Quick Description
The residential energy code provides a Standard Base Case for code compliance. It also requires that an Additional Measure be selected. There is also an allowance for log home construction.
Administration
Administration of the code is handled at each local building jurisdiction. In order to get a building permit the applicant must fulfill the requirements of the residential energy code. Both the plans and specifications must indicate how a building complies with code requirements.
Requirements
You comply with theOregon residential energy code by following the requirements specified in Table N1101.1(1). In addition to following these requirements, an Additional Measure from Table N1101.1(2) must be implemented. Code requirements are described in detail in each of the following documents:
Residential Energy Code Requirements
- Chapter 11 of the Oregon Residential Specialty Code
- Chapter 13 of the Oregon Structural Specialty Code
Standard Base Case
The following table shows the prescriptive requirements for residential code Standard Base Case. The complete version is available through your local jurisdiction, or the Oregon Department of Energy.
Table N1101.1(1) Standard Base Case
BUILDING COMPONENTS STANDARD BASE CASE
Component
|
Required
Performance
|
Std Wood
Frame Const
|
Above-Grade Walls1
|
U-0.060
|
R-21
|
Below-Grade Walls2
|
F-0.565
|
R-15
|
Flat Ceilings3
|
U-0.031
|
R-38
|
Vaulted Ceilings4
|
U-0.042
|
R-38
|
Underfloors
|
U-0.028
|
R-30
|
Slab Floor Edge Perimeter
|
F-0.520
|
R-15
|
Heated Slab Interior5
|
–
|
R-10
|
Windows & Sliding Glass Doors6
|
U-0.35
|
U-0.35
|
Maximum Allowable Window Area7
|
|
No Limit
|
Skylights < 2% heated spaces floor area8
|
–
|
–
|
Skylights > 2% heated spaces floor area
|
U-0.60
|
U-0.60
|
Exterior Doors9
|
|
U-0.20
|
Exterior Doors with >2.5 ft2 Glazing10
|
U-0.40
|
U-0.40
|
Forced Air Duct Insulation
|
|
R-8
|
1 Wall insulation requirements apply to all exterior wood framed, concrete or masonry walls that are above grade. This includes cripple walls and rim joist areas. R-19 Advanced Frame or 2x4 walls with rigid insulation may be substituted if total nominal insulation R-value is 18.5 or greater.
2 Below-grade wood, concrete or masonry walls include all walls that are below grade and do not include those portions of such walls that extend more than 24 inches above grade.
3 Insulation level for ceilings that have limited attic/rafter depth such as dormers, bay windows or similar architectural features totaling no more than 150 square feet (13.9 m2) in area per building may be reduced to not less than R-21.
4 The maximum vaulted ceiling surface area shall not be greater than 50 percent of the total heated space floor area unless area has a U-factor mp greater than U-0.031. The U-factor of 0.042 is representative of a vaulted scissor truss. A 10-inch deep rafter vaulted ceiling with R-30 insulation is U-0.033 and complies with this requirement, not to exceed 50 percent of the total heated space floor area.
5 Heated slab interior applies to concrete slab floors (both on and below grade) that incorporate a radiant heating system within the slab. Insulation shall be installed underneath the entire slab.
6 Sliding glass doors shall comply with window performance requirements. Windows exempt from testing in accordance with NF1111.2 Item 3 shall comply with window performance requirements if constructed with thermal break aluminum or wood, or vinyl, or fiberglass frames and double-pane glazing with low-emissivity coatings of 0.10 or less. Buildings designed to incorporate passive solar elements may include glazing with a U-factor greater than 0.35 by using Table N1104.1(1) to demonstrate equivalence to building envelope requirements.
7 Reduced window area may not be used as a trade-off criterion for thermal performance of any component.
8 Skylight area installed at 2% or less of total heated space floor area shall be deemed to satisfy this requirement with vinyl, wood, or thermally broken aluminum frames and double-pane glazing with low-emissivity coatings. Skylight U-factor is tested in the 20 degree overhead plane per NFRC standards.
9 A maximum of 28 square feet (2.6 m2) of exterior door per dwelling unit can have a U-factor of 0.54 or less.
10 Glazing that is either double pane with low-e coating on one surface, or triple pane shall be deemed to comply with this U-0.40 requirement.
Alternate Compliance Path
If a building does not meet the Standard Base Case, an option can be used that allows trade off between components to develop a custom path. For example: better insulated walls in order to compensate for less floor insulation than Standard Base Case requires. To apply for such credits, calculations must be completed using ORSC, Table N1104.1(1) or OSSC, Table 13-B. For more information, download pamphlet #13 of the Residential Energy Code Pamphlets.
Changes to Residential Code in 2008
Background
1992 was the last time significant changes were made to the residential energy code. The code was revised through a public process with staff support from Oregon Department of Energy and Building Codes Division.
Results
The result of that previous code changes was largely demonstrated in the 1992 Ecotope Study on code compliance in Oregon. The Oregon residential energy residential energy requirements are contained in Chapter 11 of the 2008 Oregon Residential Specialty Code. Similar requirements (but not the same at this time) are located in Chapter 13 of the 2007 Oregon Structural Specialty Code.
Code Alternatives
The code provides a Standard Base Case for compliance in Table N1101.1(1). There is also a path for log/solid timber homes. Builders must also choose an Alternate Measure from Table N1101.1(2) in order to comply with code requirements.
Walls
The code Standard Base Case requires U-0.060, which translates to R-21 batt insulation in standard wood-framed exterior walls. This is 2x6 standard construction with high-density batt or blown-in insulation with an actual R-value of 21. The Standard Base Case allows a substitution of 2x6 advanced frame construction with R-19 insulation or 2x4 construction and rigid exterior insulation with a combined insulation of R-18.5. A minimum component wall U-factor of U-0.080 may be used with thermal performance calculation method - Table N1104.1(1).
Below-Grade Walls
All heated basement walls in residential buildings must have R-15 interior or exterior insulation to the full height of the below-grade wall.
Ceilings
Flat ceilings must be insulated to a minimum of R-38. Some Additional Measures require R-49 ceiling insulation. Thermal performance calculation method requires a minimum of R-38 insulation for ceilings.
Vaults
The maximum “vaulted ceiling surface area” allowed shall not be greater than 50 percent of the “total heated space floor area” unless area has a U-factor no greater than U-0.031. The U-factor of 0.042 is representative of a vaulted scissor truss. A 10-inch deep rafter vaulted ceiling with R-30 insulation is U-0.033 and complies with this requirement, not to exceed 50 percent of the total heated space floor area.
It is not possible to achieve a performance of U-0.31 in a standard scissor truss, regardless of amount (R-value) of insulation. Unless scissor truss allows for full insulation depth across the entire ceiling, it is limited to not to exceed 50 percent of the total heated space floor area. Thermal performance calculation method would be required if the standard scissor truss exceeds 50 percent of the total heated space floor area.
Floors
Floor insulation for Standard Base Case is R-30. High-density R-30 fiberglass batt is acceptable when installed within cavity of a 4x8 post and beam floor system. Insulation as low as R-21 may be used for floors utilizing the thermal performance calculation method.
Slab on Grade Floors
Concrete slab floors that are “on grade” are required that entire perimeter to have slab edge insulation at R-15. Slab insulation must extend downward from top of slab for a minimum of 24 inches or downward to the bottom of the slab, then horizontally beneath the slab for a minimum total distance of 24 inches. Slab insulation may be reduced to R-10 using the performance calculation method.
Heated Slab Floors
For slab-on-grade floors that incorporate hydronic heating, in addition to the above perimeter insulation, the entire underside of slab must be insulated to R-10.
Windows and Sliding Glass Doors
Code requires U-0.35 for all windows and sliding glass doors. Windows that are exempt from testing in accordance with NF1111.2 Item 3 shall comply with window performance requirements if constructed with thermal break aluminum or wood, or vinyl, or fiberglass frames and double-pane glazing with low-emissivity coatings of 0.10 or less.
A minimum U-0.65 windows, sliding glass doors, doors with <2.5 ft2 glazing may be used with the thermal performance calculation method. Buildings designed to incorporate passive solar elements may include glazing with a U-factor greater than 0.35 by using Table N1104.1(1) to demonstrate equivalence to building envelope requirements.
Allowable Window Area
Code does not limit the window area in a building. Trade-off against window area is not allowed when using thermal performance calculation method.
Skylights
Skylight area installed at 2 percent or less of total heated space floor area shall be deemed to satisfy this requirement with vinyl, wood, or thermally broken aluminum frames and double-pane glazing with low-emissivity coatings. Skylight U-factor is tested in the 20 degree overhead plane per NFRC standards.
Exterior Doors
All doors must be insulated to a U-value of 0.20. For the Standard Base Case, one door up to 28 square feet may have a U-value of 0.54. An untested, solid wood door without any glazing is defaulted at U-0.54. Thermal performance calculation method requires all door U-values not to exceed 0.54.
Ducts
Duct insulation requirement is R-8. This applies to all duct systems located in non-conditioned spaces.
Heating Systems
The new code requirements contain Additional Measures, which, if selected, may require a higher performance gas-fired furnace or boiler, heat pump, or ground source heat pump. There are other Additional Measures that could be selected instead of improved heating system performance.
General
Air tightening requirements remain unchanged in the 2008 code. Vapor retarder requirements for vaulted ceilings and ceilings without an attic space above have been changed from a perm rating of 0.5 to 1.0. Check Table N1101.1(2) for various Additional Measures required. The qualifications for Additional Measure 4 are the primary heating system in a building is either: 1) zonal electric, 2) ductless furnace/heater, or 3) ductless heat pump (mini split heat pump systems). Note that this list does not include any type of hydronic heating system, even though it is possible to zone these types of systems.
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